Detection of serum M2 anti-mitochondrial antibodies by enzyme-linked immunosorbent assay is potentially less specific than by immunofluorescence.

ABSTRACT

AIM: To compare the predictive values of enzyme-linked immunosorbent assays (ELISAs) and indirect immunofluorescence (IIF) techniques for the detection of M2 anti-mitochondrial antibodies. METHODS: Commercial ELISAs are widely available for the detection of anti-mitochondrial antibody subtypes in primary biliary cirrhosis (PBC). We compared the results from two ELISAs (one recombinant, one purified antigen) with those from two IIF methods in a well-defined cohort of PBC patients and in patients with systemic lupus erythematosus, Sjögren's syndrome, sicca syndrome, systemic sclerosis, rheumatoid arthritis and blood donor controls. RESULTS: There was good correlation between a rodent substrate IIF and ELISA A (r=0.9134), but poor correlation with ELISA B (r=0.5999), which produced many false-positive results in the control population. We show that rodent IIF alone or human epithelial cell (HEp-2000) screening with confirmation by ELISA produce similar predictive values for PBC and require lesser degrees of skilled interpretation of IIF patterns. CONCLUSIONS: We conclude that the specificities of IIF are greater than the ELISA methods (99% versus 85-97%), although the ELISAs are slightly more sensitive in biopsy-proven PBC. Careful in-house validation of all new ELISA technologies is mandatory for good laboratory practice, but IIF in experienced hands remains an effective and specific assay.